The present invention relates to a control equipment for monitoring flows of drilling mud. The present equipment is suitable for application to circuits for uninterrupted mud circulation in a drilling rig. The equipment according to the present invention can control the flows of drilling mud by monitoring intrinsic parameters of the mud flows circulating in the circulation circuit included in a drilling rig. The equipment allows monitoring the drilling process during all operating phases of the drilling rig, thus acting as a safety system for both the drilling rig itself and the personnel. The present invention also relates to a method for controlling the mud circulation circuit by monitoring the intrinsic parameters of the circulating mud flows, thus allowing the drilling process to be continuously monitored during all of its operating phases and eliminating the current interruptions that occur in the drilling process when the pump is stopped before adding a stand of drill pipes.
According to the well drilling and control rules, at least two durable and reliable protection barriers must be available during the drilling process, for the purpose of preventing serious accidents such as, for example, uncontrolled leakage of hydrocarbons from the well (blowout), which might result in severe damage to people, environment, and assets.
Furthermore, the well drilling and control rules require the presence of a tested and reliable primary barrier, of the hydraulic type, consisting of drilling mud pumped through the set of pipes inserted in the well and the drill bit in wellbore, in order to facilitate the drilling process. Said mud must have a gradient greater than the gradient of the pores of the rocky formation to be drilled, so as to prevent any uncontrolled leakage of hydrocarbons or even a collapse of the drilling well. This hydraulic barrier is referred to as primary barrier.
The same rules require the presence of a secondary barrier, of the mechanical type, consisting of cemented wellbore casings and safety equipment installed at the wellhead, such as a blowout preventer, also known as BOP.
Mud circulation circuits are known from patent application US2004/178003 in which at least a part of the fluid flow coming from the main mud pump is diverted towards the mud discharge outlet in order to create a backpressure system that controls the pressure inside the annulus. According to the solutions described in the above-mentioned patent, mud circulation towards the bottom of the well is not continuous; in fact, when drill pipes need to be added or removed, the fluid flow is diverted, thus being no longer directed towards the bottom of the drilling well, and the annulus is pressurized.
It is known from patent application WO2013/060847 an inflow control device for controlling the flow of fluid into a well tubular structure arranged in a borehole, comprising a tubular part for mounting as part of the well tubular structure, an aperture provided in a wall of the tubular part, and a hollow valve organ rotatably received inside the tubular part. The hollow valve organ comprising an orifice in a wall thereof, and an outer surface of the hollow valve organ being spherical and the orifice being adapted to fluidly communicate with the aperture when the inflow control device is in an open position.
Also patent application WO2012154167 discloses a drilling system comprising a flow control device which can regulate the mud flow from a rig pump to a drill string. The device is interconnected between the pump and the manifold for controlling the mud directed into the pipe strings arranged in the wellbore. Another control device regulates the flow through a line in communication with the annulus.
Patent application US20060157282 describes equipment, associated with the drill strings, which can pressurize the annulus as a function of the density of the mud directed towards the well bottom and of the mud coming up from the well bottom. This kit is arranged in the drill pipes and may suffer damage while creating the well itself, thus becoming useless.
Patent application US2013180735 discloses equipment for annulus pressurization, which is associated with the drill pipes and arranged inside the wellbore. Like the above-mentioned patent application, this kit is inserted in the wellbore and requires that a fixed device be installed therein.
Finally, also patent application WO2013060847 describes a kit to be positioned inside the wellbore.
Patent application EP2749854 describes a computer system provided with a processor and a memory medium that can be read by the processor. The memory stores instructions which, when executed, allow the processor to receive a first reference density measured at a first pressure and a second reference density measured at a second pressure. The first and second density values are measured at a reference temperature. The measurements are carried out by using measuring devices operating on the Coriolis principle.
All of the above-mentioned solutions are applied to circulation systems wherein mud inflow towards the well bottom is interrupted during the steps of adding or removing drill pipes.
All of the above-mentioned solutions cause a very sudden and long-lasting pressure variation at the well bottom while connecting or disconnecting pipes to/from the drill string. In particular, due to the turning on/off of the pumps for circulating the mud at the bottom of the well, pressure variations occur which can destabilize the well itself, which may result in serious damage to people, environment and assets.
The solutions known in the art utilize the Coriolis principle for determining the flow rate of the fluid in the mud circulation circuit. This technological solution, though very accurate, suffers from reliability problems in that said system is easily subject to clogging, in which case it will stop working. This will result in wasted time and higher maintenance costs.